Each autumn, the island of Corvo, the smallest and northernmost in Portugal’s Azores archipelago, darkens its lights for five nights in a conservation effort aimed at protecting Cory’s shearwaters, a seabird species native to the Atlantic Ocean. Since 2019, the island’s approximately 450 residents have voluntarily participated in this blackout to mitigate the harmful effects of artificial lighting on the young seabirds as they embark on their first flight to the ocean.

The initiative traces its roots back to 1991, when locals observed increasing mortality rates among juvenile Cory’s shearwaters. These young birds spend around three months in their nests before taking flight, using the stars to navigate toward the sea. However, the glow of streetlights in Vila do Corvo, the island’s only village, disorients many fledglings, causing them to crash into buildings and streets.

In response, villagers began nocturnal rescues, searching darkened streets to recover and care for the fallen birds. This local effort inspired broader conservation campaigns, leading the Azorean government to launch the “SOS Cagarro” program in 1995, extending protective measures to the other eight islands in the archipelago. The Portuguese Society for the Study of Birds (SPEA) later joined the initiative, enhancing its reach and impact.

During the annual blackout, public lights are switched off, though household lights are not required to be turned off, with many residents choosing to minimize their use nonetheless. The island’s darkness allows the stars to become clearly visible, guiding fledglings toward the ocean with less confusion from artificial illumination. Volunteers, often working late into the night, patrol the village to locate and rescue disoriented birds. Rescued shearwaters are placed in cardboard boxes to recover overnight and are released the following day from cliffs overlooking the sea, giving them a second chance to survive.

The campaign reports that since 2015, over 30,000 Cory’s shearwater fledglings have been rescued across the Azores, with approximately 6,000 saved on Corvo alone. Corvo remains the only island in the archipelago to enact a complete public lighting blackout as part of these efforts.

Forest ranger Rui Pimentel and volunteers, including young local participants like Leonardo Xavier, are instrumental in these conservation activities. SPEA has also implemented measures such as ultrasonic devices near nests to deter predators, particularly cats, which pose a significant threat to shearwater chicks.

Marine biologist Tania Pipa from SPEA, who travels annually from São Miguel Island to monitor nests on Corvo, highlights the significance of the birds to the region’s biodiversity. “To me, the day I don’t hear Cory’s shearwaters in the Azores, it will certainly not be the Azores,” she said.

The Corvo blackout demonstrates how coordinated local action and community engagement can reduce light pollution’s impact on wildlife. It serves as an example of how small adjustments in human behavior can support biodiversity and foster coexistence with natural ecosystems.